Forest Preserve District of Cook County, Illinois
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The Plants of Vacant Lots
Nature Bulletin No. 391-A   October 17, 1970
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

THE PLANTS OF VACANT LOTS
If all vacant lots could be turned into well-tended gardens or smooth grassy playgrounds, it would be a fine thing. However, in cities and town, their topsoil has been either removed or so disturbed and abused by digging and filling that little will grow except the toughest of plants - - weeds, that thrive on neglect. Because these weeds are the same ones that make us so much work and trouble around our homes, gardens and farms, we hate them.

A weed is merely a plant growing where it is not wanted. Weeds have bold aggressive plant personalities, each kind with striking, easily recognized features. Where there are weeds there is also a host of insects and other small animal life such as slugs, snails, pillbugs, centipedes and worms. Native birds and small mammals, too, find food and shelter there. In fact, a weedy vacant lot offers unusual opportunities for interesting studies in nature. One can be found within five minutes walk of almost any school in metropolitan Chicago. They should be used to add life to science courses which too often depend too much on dried plants, dried insects, and drier books.

After the wreckage had been cleared away following the air raids over London in 1940 and 1941, there were a number of news stories about botanists finding plants growing there which had not been seen near London for over a century. The same sort of thing happens in our forest preserves when we plow strips to stop the spread of fire. These fire lanes do not grow up in the kinds of plants native to our woodlands and prairies but with the common weeds of farms and gardens.

These plants which come into newly broken or cultivated soil are, with a few exceptions such as the ragweeds, all foreign plants. The seeds of most of them were brought to this country in colonial times -- mixed with garden seeds, in cattle feed, in packing materials, or as stowaways. Most of them arrived in America free of their natural enemies in the Old World and found few native plants equipped to offer much competition to their rapid spread in cultivated soil. They spread westward with the early settlers. In Illinois, sandburs popped up along the Sangamon River in the 1830's. By 1852, black mustard, sheperd's purse, purslane, wild parsnip, mullein, hemp and several foreign grasses were growing near Peoria. Each decade has seen the arrival of others.

Weeds produce large numbers of seeds, usually quite small, often lying dormant for many years. Counts of the average numbers of seeds from a single full-grown plant give such figures as: dandelion, 1792; cocklebur, 9700; ragweed, 23,100; purslane, 69,000; pigweed, 85,000; crabgrass, 89,600; and foxtail, 113,600.

Different weeds scatter their seeds in different ways. Those of milkweeds and thistles are airborne; velvet-leaf and pigweed seeds drift with snow or slide over ice; old-witch grass and Russian thistle are tumbleweeds; the giant ragweed, bindweed and smartweed seeds are carried by water; birds carry the berries of nightshade, the seed pods of pepper grass and, in mud on their feet, almost any kind. Burdock, cocklebur, and dozens more, cling to the coats of animals; but the long distance travelers ride with man himself.

A weed has also been defined as a plant for which we have discovered no use, and certainly some of them seem unpromising. Too many are either stringy, bitter, smelly, prickly, fuzzy, poisonous, or give us hay fever. On the credit side, many have gay flowers, some make fine salad greens, and a few yield useful drugs.

Best of all, they give first aid to injured soil and prevent erosion.


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